The bioengineering is in a constant search of substitutes capable of replacing the autologous bone graft.
In developing such materials it is possible to find different bioceramic based products which try to imitate the natural bone, for example document EP0329098 reveals a curable material comprising hydroxyapatite, zinc oxide and/or magnesium oxide, which hardens in a period of 2 to 19 minutes, and maintains a pH in the range of 6 to 8. While this range of pH can be considered as physiological, the hardening interval is too wide, since 2 minutes is just a very short time to achieve a correct placement and a good molding of the material and 19 minutes is too much time for the operation needs in bone surgery.
In addition, the hydroxyapatite, although it is a material with adequate ostoconductive characteristics, features incorporation problems due to the fact that its reabsorption is carried out very slowly.
Document EP0555807 teaches a substitute comprising bovine apatites (Xenograft), mixed with calcium oxide, zinc oxide, magnesium oxide and chitosan. This products exhibits a pH in the range from 6 to 8, which interval can be considered as similar to physiological, the hardening times are prolonged. The product is based on the bovine apatite system, which has excellent osteoconductive properties. However, given the precedence of the apatite, this is not exempt of biohazards and increased the costs of production due to the high costs associated with its processing.
The application U.S. Pat. No. 5,618,339 teaches a bone filler which incorporates an osteoinductive substance. The composed disclosed therein is formed by crystallized hydroxyapatite and amorphous hydroxyapatite, mixed with chitosan. The amorphous substance is obtained from animal bone tissue (bovine), which makes the obtaining process of products from animal species to be wasteful, expensive and not exempt of biohazard.
According to such document, the composite features hardening properties and handles a pH in a physiological range. The base product is hydroxyapatite, which is recognized by its excellent osteoconductivity, but as mentioned above, its origin from the tissue of different species (Xenograft) causes this product to exhibit the same disadvantages as those in the above reference.
According to the same document, the osctoinductive property was tested in experimental defects created in rat calvarial Sprague Dawley, females of 4 weeks old, in a skull defect of 2 mm diameter and a depth of 0.3 mm. It was compared with control defects containing only hydroxyapatite, finding thereby differences in the bone formation. However, as it is sufficiently reported in the specialized literature, in order to test osteoinductive or osteoprmotive properties the defects should be of 5 mm diameter and 0.88 mm depth so as to be qualified as “critical size defects”.
In this regard, there is still a non-fulfilled need in the state of the art of a ceramic material featuring the proper physicochemical characteristics which allow an easy molding and setting of the material in order to facilitate the application thereof in bone cavities with difficult healing.